Door for a piano case having arrangement for tonal escapement



United States Patent Inventor John B. Hahig Jasper, Indiana App]. No. 748,098

Filed July 26, 1968 Patented Oct. 27, 1970 Assignee Kimball Piano & Organ Co., Jasper, Indiana a corporation of Indiana DOOR FOR A PIANO CASE HAVING ARRANGEMENT FOR TONAL ESCAPEMENT Primary Examiner-Richard B. Wilkinson Assistant Examiner-John F. Gonzales Attorney-Melvin A. Crosby ABSTRACT: Piano case for spinet and upright type pianos having one or more forwardly facing closure doors. At least one of the doors has a large opening and an auxiliary panel of relatively thin material is supported in spaced relation to the opening so that the vibrations from the strings of the piano will vibrate the panel, while there is a gap between the closure door and the panel around the edges of the panel through which sound vibrations can pass to the region in front of the piano Optionally, an auxiliary resonance chamber can be mounted on the inside of the panel, preferably in the region near the bass strings.

Patentd Get. 27, 1970' v vINVENTOR. -,JOHN B. R Q

DOOR FOR A PIANO CASE HAVING ARRANGEMENT FOR TONAL ESCAPEMENT The present invention relates to pianos and particularly to an arrangement for improving the tonal qualities and sound projection thereof.

In pianos of the type in which the strings are arranged in a vertical plane, namely, in upright and spinet pianos, the sound that emanates from the piano toward the front is principally derived from openings and louvres provided in the upper portion of the piano case. Many times it is merely the upper closure door, or swing assembly of the piano above the keyboard that is tilted outwardly to permit sound to emanate from the front of the piano. In other cases, the top wall of the piano case is arranged so that it can be pivoted upwardly to a partly open position to permit sound to be projected toward the front of the piano.

It has been attempted to augment the sound projected from the front of the piano by making the lower closure door relatively thin, or by making the lower closure door in the form of an extremely thin panel in a supporting frame. One such attempt is disclosed in the US. Pat. to Heppe No. 71 1,765. None of these attempts have been attended with any great success, however, so that heretofore, the region toward the front of the piano has been somewhat defective in the production of sound of the best quality and volume. In particular, the player of a piano of the nature referred to is located in a position where the true sound of the piano cannot be heard properly.

Having the foregoing in mind, it is a primary objective of the present invention to provide a piano case, especially for spinet and upright type pianos, in which improved projection of sound toward the front of the piano is obtained.

A still further object is the provision of a piano structure in which improved projection toward the front of the piano is obtained without any substantial change in the overall structure of the piano except in connection with one or more of the forwardly facing closure doors of the piano case.

A further object of the present invention is the provision of a spinet or upright piano construction in which there is improved quality as well as improved volume of the sound pro jected from the piano toward the front thereof.

The objectives of the present invention are obtained, in brief, by providing a large opening in at least one of the forwardly facing closure doors of the piano case, and mounting a panel larger than the opening in spaced relation with the opening and parallel with the respective closure door, and suspending the panel on the closure door or member by spaced supporting posts so as to leave a gap between the panel and the adjacent part of the closure door or member through which sound can pass in an unobstructed manner.

The panel is thin enough that it will be set into vibration by the vibrations from the piano strings and from the major sound board of the piano at the back and there may also be included on the string side of the panel an auxiliary resonance chamber which will augment the tones within a predetermined frequency range, preferably the tenor range.

The objectives of the present invention referred to above, as well as still other objects and advantages thereof will become more apparent upon reference to the following detailed specification taken in connection with the accompanying drawings, in which:

FIG. 1 is a perspective view of a spmet type upright piano having a lower closure member constructed according to the present invention mounted thereon;

FIG. 2 is a perspective view, partly broken away, looking in at the closure member of the piano from the front thereof;

FIG. 3 is a vertical sectional view through the novel closure member of the present invention and is indicated by a section line III-III on FIG. 2;

FIG. 4 is a fragmentary perspective view of an auxiliary panel according to the present invention having resonance chamber mounted on the back thereof;

FIG. 5 is a fragmentary perspective view looking in at the resonance chamber from the panel side thereof to show more in detail the construction of the resonance chamber; and

FIG. 6 is a vertical sectional view showing how the upper closure door, or swing assembly, of an upright piano shown above the piano keyboard could be constructed so as to embody the present invention.

Referring to the drawings somewhat more in detail, FIG. 1 shows a spinet piano having a case 10. The soundboard and strings are conventionally arranged vertically toward the back of the piano case 10. Below the keyboard 12 of the piano is a forwardly directed closure door or member 14, retained in place in a conventional manner such as by locating pins at the bottom and a spring clip at the top.

Closure member 14, as will be seen in FIGS. 2 and 3, taken in connection with FIG. 1, is in the form of an outer frame 16 defining a large central rectangular opening 18.

According to the present invention, a relatively thin panel 24 is arranged in spaced parallel relation with lower closure member 16 toward the outside of the piano case and is supported on the lower closure member by the posts 26 which are fastened to both the lower closure member and the panel in any suitable manner. As will be seen in FIGS. 2 and 3, the posts 26 are spaced inwardly from the edges of the panel 24.

Closure member 14 may have a frame made up of strips about 3 inches wide and the opening therein, for one size piano, is on the order of about 48 by 12 inches. The panel 24 is of such a size to extend about an inch beyond the limits of opening 18 in all directions. The posts 26, in practice. may have a cross-sectional shape of about 2 inches by threequarter inches and are set inwardly from the opposite short ends and top and bottom edges of the panel so as to leave about 2 inches or more of the ends and about 1 inch of the top and bottom edges of the panel 24 unsupported. The specific dimensions given are, of course, exemplary only. The total area of the panel engaged by posts 26 is relatively small so that the panel is free to vibrate over substantially its entire surface area.

Preferably, the outer face and edge of the panel is finished so as to harmonize with the finish on the piano case, although a decorative fabric covering could be applied over the area of the panel and the gap thereabout, if desired.

It will be appreciated that. in addition to the sound projected toward the front of the piano due to the panel vibrating, sound will also pass through the opening 18 and around the edges of the panel.

It is found that a piano constructed according to the present invention. as opposed to a conventional piano having the usual solid closure door. is characterized in increased volume of sound projected toward the front of the piano, less harsh tones, and a sound of more pleasing quality. The sound is noticeably louder to the human ear and appears to be of substantially the same volume as when the bottom closure door of the piano is completely removed.

It has also been found that, in addition to increased volume of sound toward the front of the piano, the tone is modified so as to produce what could be referred to as a more mellow tone. The tenor section of the piano is more clearly brought out than with a solid door, or with no door at all on the lower part of the piano. The harsh nonharmonically related overtones which can be produced by piano strings when struck by hammers, are much less pronounced with the special door than when no door at all is on the piano. The sound projected toward the front of the piano is thus louder and more full and less harsh than with a standard solid closure door, and is fuller and less harsh and more pleasing to the car than when the closure door is completely removed from the piano.

As to the improved projection of tone from the piano toward the front of the piano, the sound can pass through the special door construction of the present invention about the edges of the thin panel of the special door and is not in any way muffled as is the case when a solid door is employed on the piano. The panel is of a material quite similar to that used in piano sound boards, and is quite easily set into sympathetic vibration by the acoustic waves set up within the piano by the piano sound board and strings. Since the panel is not rigidly bound at the edges, it is free to vibrate at all the frequencies developed in the piano. The panel, as mounted according to the present invention, thus does not have the blocking effect on the internal acoustic waves as does the standard solid doors which are conventionally used in pianos.

The total effect is that of a more spacious sound which does not seem to emanate from a rather small point source. This effect is particularly noticeable to the piano player because, with the special door, the source of sound is not predominantly from louvers or escapement openings above the keyboard but is also from below the keyboard and appears to be rather general as to source. While a standard lower closure door does not entirely restrict sound from beneath the keyboard, the area through which sound can pass freely is volume at the treble end of the piano scale. The openings about the edge of the panel also serve as tone chamber ports for the bass frequencies while the cabinet structure of the piano and the bottom door serve to create somewhat of a resonance chamber. The relative port area creates what can be termed a low Q, broadly tuned, chamber and this tends to produce a fuller and more mellow tones which have been referred to and deemphasizes the harsher tones also referred to above.

FIGS. 4 and 5 show a modification particularly adapted for creating enhancement of frequencies in a certain range, especially in the tenor range, with no depreciation of the tone or volume of the base and treble ranges. Various shapes and materials and openings into the chamber and mounting configurations can be employed and the particular auxiliary resonance chamber illustrated in FIGS. 4 and 5 is merely exemplary what could be used in this connection.

The auxiliary chamber comprises a member 31), of plywood for example, formed to a channel shape, and end members 32 are set into the formed channel shaped member 30. Posts 34 are employed for supporting the auxiliary resonance chamber in spaced parallel relationship with the leads of the panel. There may be, for example, a small gap, say, about one-fourth inch, between the open side of the auxiliary resonance chamber and the back of the panel. The auxiliary resonance chamber may also be provided with port openings which are designated at 36 if so desired. The chamber is preferably located toward the base end of the panelv The provision of the auxiliary resonance chamber provides for tone enhancement, particularly in the tenor region, and it is noted that the aforementioned harsh tones produced upon the striking of a string seem to be diminished somewhat while a slightly fuller bass tone is obtained by the use of the auxiliary resonance chamber described.

By way of example, a resonance chamber measuring about 8% inches by 23 inches by 3% inches was mounted on the inside of the panel 24 toward the bass end thereof and spaced about one-quarter of an inch therefrom and with two supporting posts at the ends as illustrated in FIGS. 4 and 5. The audi ble tests conducted showed the aforementioned superiority of tone in the tenor region and no loss of tone or volume in the bass or treble regions. The effects were readily detectable by the human ear.

As will be seen in FIG. 6, the swing assembly for an upright piano can also be constructed in conformity with the present invention. In FIG. 6, frame 50 is generally concave toward the front of the piano and has an opening 52. Thin panel 543 in front of opening 52, and larger than the opening, is supported by relatively small posts 56 connected to spaced points on the back of the panel and extending into the opening 52 and attached to the frame 50. Panel 54 is, of course, finished to harmonize with the finish on the piano case.

The thin panels and apertured closure doors may be used as the lower closure doors of spinet pianos, or as either or both of the lower and upper closure doors of an upright piano. The

panels may be substantially the full length of a closure door for small pianos but may be shorter for larger pianos.

Either the lower closure door or upper closure door, the latter being referred to as a swing assembly, can be incorporated in new manufacture or supplied as replacement for the closure doors existing on pianos.

it will be understood that this invention is susceptible to modification in order to adapt it to different usages and conditions; and accordingly, it is desired to comprehend such modifications within this invention as may fall within the scope of the appended claims.

I claim:

i. In an upright type piano having a case with a front closure door on the front of the case beneath the keyboard of the piano and spaced forwardly from the strings and sound board of the piano, a large opening formed in said closure door extending over the major portion of the width and height thereof, a relatively thin stiff panel in spaced parallel relation to said opening and supported solely by and in spaced relation to said closure door so as to leave an open gap between the panel and closure door extending substantially completely around the periphery of the said panel.

2. A piano according to claim 1, in which said panel extends beyond the limits of said opening in all directions.

3. A piano according to claim I, which includes support posts connected to said panel at spaced points thereon and extending from the panel to said closure door and connected to the closure door so the panel is supported directly on the do sure door and forms a unit therewith.

4. A piano according to claim 3, in which the surface of the region of said closure door means which is located directly behind the marginal portion of said panel is divergent toward said panel.

5. A piano according to claim 3, in which said posts extend into said opening and are connected to said closure door means at the periphery of said opening, said posts being located inwardly from the marginal edges of said panel.

6. A piano according to claim 1, which includes means forming a resonance chamber mounted on the string side of said panel, said resonance chamber comprising a boxlike member open on the side facing said panel and substantially smaller than said panel, said open side of said resonance chamber being disposed in spaced parallel relation to said panel, and spaced support members extending between the panel and the resonance chamber and supporting the latter on the panel.

7. A piano according to claim 5, in which said support members are postlike elements of relatively small cross-sectional area and in spaced relation so as not materially to inhibit vibration of said panel.

8. A piano according to claim 6, which includes aperture means formed in the wall of said resonance chamber which faces said strings.

9. A piano according to claim 6, in which said resonance chamber is positioned on said panel so as to be nearest to the end of the panel disposed nearest the bass strings of the piano.

10. A piano according to claim 1, in which said opening and said panel are rectangular. 

